Berkshire Hathaway created a buzz when it invested in China-based BYD Company (BYDDF) in 2008 back when the company was still an obscure startup.

Today, BYD has become the global leader in electrical vehicle (EV) production, selling more vehicles than Tesla (TSLA) last year.

After meeting BYD CEO Wang Chuanfu, Berkshire proceeded to take a 10% stake in BYD for $230 million. Its stake is now worth about $1.23 billion. That’s an annual return of over 24% per year, making BYD Berkshire’s top investment over the last decade.

BYD Company — the initials stand for “Build Your Dreams” — was founded in 1995 as a battery company, supplying mobile phone batteries. In 2002, BYD expanded into electric vehicles (EVs).

Today, BYD is the largest rechargeable battery maker in the world, boasting a 25% market share. Its 2015 sales topped $12.3 billion — a year-on-year increase of 37.8%.

A big chunk of BYD’s success is thanks to the Chinese government, which has set out a plan to both cut down on emissions and pollution.

China has ramped up its investment in building a vast network of recharging stations. It also offers outright subsidies to keep EVs’ prices on par with their gasoline-driven counterparts.

In Shenzhen, the local government has bought more than 4,000 of BYD’s EV buses. Home province Guangdong has also placed orders for 6,432 buses.

Meanwhile, BYD has sold its mass-produced, fully electric buses, in over 110 cities in 36 countries.

BYD is quietly building a US business supplying rechargeable buses to environmentally minded transit agencies such as Los Angeles and Long Beach.

BYD buses are in use at Amsterdam’s Schiphol Airport and in Japan, Hong Kong, Finland, Denmark, Uruguay, Spain, Germany, Canada and Brazil.

With sales of EVs expected to triple in 2016, the prospects for BYD are only getting stronger